An exhaust heat recovery device is known in which exhaust heat is recovered by performing heat exchange between exhaust gases from an internal combustion engine as a high-temperature fluid and cooling water of the internal combustion engine as a low-temperature fluid (see Patent Document 1).
The exhaust heat recovery device disclosed in Patent Document 1 comprises an exhaust pipe, a shell member, a heat exchange portion, an exhaust gas inflow portion, and a valve. The exhaust pipe is a member formed in a tubular shape and guides exhaust gases from the internal combustion engine to the downstream side. The shell member is a tubular member that covers the outside of the exhaust pipe. The heat exchange portion has a heat exchanger disposed between the exhaust pipe and the shell member. The heat exchanger performs heat exchange between exhaust gases as a high-temperature fluid and a low-temperature fluid flowing inside thereof.
The exhaust inflow portion in Patent Document 1 is a portion where exhaust gases flowing out of the exhaust pipe enters the heat exchange portion. The exhaust gas inflow portion in Patent Document 1 is an opening formed in the upstream side of the downstream-side end portion of the heat exchanger along the flow path for exhaust gases in the exhaust pipe and formed along the entire circumference of the exhaust pipe.
The valve is disposed in the downstream side of the exhaust gas inflow portion along the flow path for exhaust gases in the exhaust pipe.
Specifically, in the exhaust heat recovery device, the valve is closed to close the exhaust pipe when the temperature of the cooling water of the internal combustion engine is low. Accordingly, exhaust gases from the internal combustion engine enter the heat exchange portion from the exhaust gas inflow portion and heat exchange is performed in the heat exchange portion with the cooling water.
On the other hand, in the exhaust heat recovery device, the valve is opened to open the exhaust pipe when the temperature of the cooling water of the internal combustion engine is high. Accordingly, in the exhaust heat recovery device, the flow rate of exhaust gases entering the heat exchange portion from the exhaust inflow portion is decreased so as to reduce heat transfer from the exhaust heat to the cooling water.